My daughter has made dozens of lapbooks over the years. (You can see all her lapbook pictures at Flickr.) She started back in Kindergarten and made them all the way through sixth grade. Now in seventh grade, she has switched to notebooking as her preferred way to narrate her lessons, but she sometimes still incorporates minibooks into her notebooking pages.
Lapbooks are rather hard to describe in words simply because there are so many ways to make lapbooks. At their foundation, lapbooks are a collection of minibooks, all centered around a unifying theme.
Normally the minibooks have unique folds and ways to organize information — trifold, wheel book, layered book, matchbook, three square unfolding book, envelope book, and many more. For children who like papercrafts, creating the minibook folds is fun.
At the end of each lesson, the child makes a minibook about what he learned. At the end of the whole unit study on that topic, all the minibooks are gathered and affixed onto a file folder that has been refolded with a shutterfold.
I am a proponent of DIY lapbooking because I feel that it allows for more flexibility, creativity, and learning than a pre-purchased kit. But buy a kit or two in the beginning to get the feel for how the minibooks work with your unit of study. After some experience, you will be able to plan your own lapbooks, pulling from a variety of resources such as the books shown above.
I always liked keeping a stash of blank minibooks on hand for daily narrations.
From my perspective, lapbooking is a form of narration that fits in well with a Charlotte Mason homeschool. Although lapbooking is a tool in our toolkit, it is not something that controls our curriculum.
Have more questions about lapbooking? They are probably answered at Lapbooking FAQ & Polls. If not, feel free to leave a comment here and I will reply.